* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}
ul,
li {
  list-style: none;
}
.accordion {
  display: flex;
  width: 600px;
  height: 200px;
}
.accordion li {
  flex: 1;
  cursor: pointer;
  line-height: 200px;
  text-align: center;
  transition: flex 500ms;
}
.accordion li:nth-child(1) {
  background-color: #fff;
}
.accordion li:nth-child(2) {
  background-color: #000;
  color: #fff;
}
.accordion li:nth-child(3) {
  background-color: #fff;
}
.accordion li:nth-child(4) {
  background-color: #000;
  color: #fff;
}
.accordion li:nth-child(5) {
  background-color: #fff;
}
.accordion li:nth-child(6) {
  background-color: #000;
  color: #fff;
}
.accordion li:hover {
  flex: 2;
}
